This project investigates the nature of rehearsal processes that animals use to maintain information in short-term memory (STM) and how rehearsal is related to associative learning. Most experiments use delayed matching-to-sample tasks in which sample events are reinforcement and nonreinforcement. Initial results indicate that rehearsal may be disrupted (as assessed by performance losses) by changes in delay-interval illumination while the same illumination has no effect on association formation when it occurs after discrimination learning trials. Experiments are planned to determine why the illumination has such disruptive effects. Another line of research has resulted in the development of an animal model of directed forgetting; stimuli normally signaling the absence of tests of STM in delayed matching were found to reduce the accuracy of performance. The reasons for this effect will be explored. Finally, generalization of some of these results to rats will be attempted pending development of techniques for the study of rats' STM.